text: /*=========================================================================
   *
   *  Copyright Insight Software Consortium
   *
   *  Licensed under the Apache License, Version 2.0 (the "License");
   *  you may not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *         http://www.apache.org/licenses/LICENSE-2.0.txt
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   *=========================================================================*/
  
  #include "itkConvolutionImageFilter.h"
  #include "itkImageFileReader.h"
  #include "itkImageFileWriter.h"
  
  int itkConvolutionImageFilterDeltaFunctionTest(int argc, char * argv[])
  {
    if ( argc < 3 )
      {
      std::cout << "Usage: " << argv[0] << " kernelImage outputImage" << std::endl;
      return EXIT_FAILURE;
      }
  
    const unsigned int ImageDimension = 2;
  
    typedef unsigned char                            PixelType;
    typedef itk::Image< PixelType, ImageDimension >  ImageType;
    typedef itk::ImageFileReader< ImageType >        ReaderType;
  
    // Read kernel image.
    ReaderType::Pointer reader = ReaderType::New();
    reader->SetFileName( argv[1] );
    reader->Update();
  
    // Set up delta function image.
    ImageType::RegionType region = reader->GetOutput()->GetLargestPossibleRegion();
    ImageType::Pointer deltaFunctionImage = ImageType::New();
    deltaFunctionImage->SetRegions( region );
    deltaFunctionImage->Allocate(true); // initialize
                                                               // buffer
                                                               // to zero
  
    // Set the middle pixel (rounded up) to 1.
    ImageType::IndexType middleIndex;
    for ( unsigned int i = 0; i < ImageDimension; ++i )
      {
      ImageType::SizeValueType sizeInDimension = region.GetSize()[i];
      middleIndex[i] =
        itk::Math::Floor< ImageType::IndexValueType >( 0.5 * sizeInDimension );
      }
    deltaFunctionImage->SetPixel( middleIndex, 1 );
  
    typedef itk::ConvolutionImageFilter<ImageType> ConvolutionFilterType;
    ConvolutionFilterType::Pointer convolver
      = ConvolutionFilterType::New();
    convolver->SetInput( deltaFunctionImage );
    convolver->SetKernelImage( reader->GetOutput() );
  
    typedef itk::ImageFileWriter<ImageType> WriterType;
    WriterType::Pointer writer = WriterType::New();
    writer->SetFileName( argv[2] );
    writer->SetInput( convolver->GetOutput() );
  
    try
      {
      writer->Update();
      }
    catch ( itk::ExceptionObject & excp )
      {
      std::cerr << excp << std::endl;
      return EXIT_FAILURE;
      }
  
    return EXIT_SUCCESS;
  }
  